1. Field of the Invention
The invention is related to the field of communication networks and, in particular, to synchronizing call feature data between an IMS network and a legacy network, such as a cellular network.
2. Statement of the Problem
Wireless phone providers are developing dual mode phones that have the functionality for communicating with a cellular network (e.g., CDMA or GSM) and another type of wireless data network, such as a WiFi network (e.g., 802.11b, 802.11g, etc). The concept of the dual mode phone is to allow a user the flexibility to communicate with either the cellular network or the wireless data network. The wireless data networks are typically used for data communications such as Internet browsing, email, etc, but may also be used for voice communications in the form of VoIP calls. Cellular networks are typically used for voice communications, but have also been adapted for data communications.
When a dual mode phone is in range of the cellular network, the dual mode phone registers with the cellular network to receive communication access. The user may subscribe to call features offered by the cellular service provider, such as call forwarding, call waiting, caller ID, etc. The call features subscribed to by the user are typically recorded in a user profile that is stored in a Home Location Register (HLR) in the cellular network. Some of these call features may be changed or updated by the user through his/her dual mode phone, through a web page, etc. For example, the user may change a call forwarding directory number to allow calls to the dual mode phone to be routed to an office phone. When the user changes a call feature, the cellular network updates the user profile in the HLR to reflect the change.
In addition to cellular networks, dual mode phones may come into range of local wireless “hot spots” in a corporation or enterprise, airports, book stores, coffee shops, etc. The wireless hot spot may be in a building where cellular service is unavailable or may overlap a cellular service area. When a dual mode phone is in range of a wireless hot spot, the dual mode phone registers with an IP Multimedia Subsystem (IMS) core network via the Wireless LAN (WLAN) to receive communication access. The IP Multimedia Subsystem (IMS) core network can provide call features similar to the call features offered by the cellular network.
An IMS network includes a Home Subscriber Server (HSS) that is a master database that stores user profiles, performs authentication and authorization of the user, and provides information about the physical location of the user. Call features, such as call forwarding, call waiting, caller ID, etc, are provided in the IMS network by application servers (AS). Again, some of these call features provided by the application servers may be changed or updated by the user through his/her dual mode phone, through a web page, etc, and the change to the call feature is stored in the appropriate application server. For instance, if a user changes call forwarding busy digits, then the application server providing the call forwarding busy feature stores these digits for the user.
The application servers communicate with the HSS over the Diameter Sh interface to extract the necessary feature data to dispatch the logic of a call feature. The Diameter Sh interface defines two types of data: transparent and non-transparent. Transparent data is data that an application server may define and transmit to the HSS for storage. The HSS does not normally interpret or otherwise process the transparent data but blindly stores the data in a repository until the application server retrieves the data. Non-transparent data is data that is explicitly defined as readable, but cannot be changed by application server. It may have an HSS role defined for other HSS interfaces (registration or provisioning) and therefore the HSS has knowledge of the content.
A dual mode phone should provide similar call features regardless of whether access is through the cellular network or the wireless data network (e.g., IMS network). However, a problem may occur if the user changes one or more of the call features. If access of the dual mode phone is through the cellular network, then the call feature change will be made in the cellular network and stored in the HLR. If access of the dual mode phone is through the IMS network, then the call feature change will be made in the IMS network and stored in the application server that is providing the call feature and/or the HSS.
Unfortunately, there is presently no efficient mechanism to synchronize call feature changes between the cellular network (or other legacy networks) and an IMS network. Presently, an application server may query an HLR for data updates, but the interface (typically MAP) between the application server and the HLR is insufficient to provide the notifications required to synchronize the call feature changes. As a consequence, an application server in the IMS network that is adapted to provide a call feature to a user may not be notified of a change to the call feature in the cellular network. Similarly, the HLR in the cellular network may not be notified of a change to the call feature in the IMS network. A user of a dual mode phone may unfortunately not receive consistent call features from the cellular network and the IMS network.